Concentrate of polyfunctional compounds usable for the preparation of foamed polyester materials

Abstract

A masterbatch composition comprising an aromatic polyester resin, a polyolefin and a polyfunctional compound selected from the dianhydrides of tetracarboxylic aromatic and / or aliphatic acids and the polyepoxidic compounds, wherein the polyester resin and the polyfunctional compounds are omogeneously dispersed as solids in a matrix formed by the polyolefin, as domains of average particle size less than 800μ. The masterbatch is prepared by milling polyester resins and polyolefin granules to obtain powders having average particle size of less than 200μ, and the powders are therafter homogeneously mixed.

Description

[0001]The present invention relates to a polymeric concentrate (masterbatch), usable for the production of foamed aromatic polyester resins, capable of imparting to the polyester the rheological properties suitable for the production of foamed articles directly in the foaming process and the process for the production of the masterbatch.BACKGROUND OF THE INVENTION[0002]The technology widely used for the production in large scale of foamed polyester articles uses as starting material a resin grade which has already intrinsic properties for being foamed, and in that grade, the resin is sold to the producers of foamed articles.[0003]In the patent literature there are described polymeric masterbatches suitable for the production of foamed polyester articles using as starting polyester resin standard bottle grade PET having intrinsic viscosity of about 0.8-0.9 dl / g. None of said masterbatches have, up to now, found industrial scale application due to some drawbacks so far unremoved.[0004...

AI Technical Summary

Benefits of technology

[0006]It has now been surprisingly found that it is possible to obtain a masterbatch that not only prevents the problems above mentioned, but also allows to significantly improve its performance. The masterbatch is obtained from a mixture of an aromatic polyester, resin, a polyolefin and a polyfunctional compound hereinafter specified, wherein the polymeric components of the mixture are subjected to a specific treatment prior being used for the masterbatch preparation. The polyester and the polyolefin as produced and commercialized are in a granular shape. According to the present invention, the granules are milled to obtain an average particle size of less than 800μ, preferably less than 200μ, with at least 80% of the particles having a size less than 200μ. The milled granules are then mixed with the polyfunctional compound (which is already as powder with particle size less than 200μ) to obtain a homogeneous mixture. The mixture is then dried and used for the masterbatch preparation.

Problems solved by technology

None of said masterbatches have, up to now, found industrial scale application due to some drawbacks so far unremoved.

The above problems lead to instability in the foaming process with the production of an uneven foam quality.

This masterbatch has limitation in the poor PMDA dispersion and in the high amount of polyolefin added to the foamable mixture, which impairs some of the peculiar characteristics of a foamed polyester article, such as the thermal and dimensional stability.

Moreover the masterbatch cannot be easily dried prior its use due to sticking problems caused by the low softening point of the polyolefins, which further reduce the efficiency of PMDA in the foaming process.